This book constitutes the joint refereed proceedings of the 5th COST264 International Workshop on Networked Group Communications, NGC 2003, and the 3rd International Workshop on Internet Charging and QoS Technologies, ICQT 2003, held in Munich, Germany, in September 2003.The 25 revised full papers and 6 revised short papers presented were carefully reviewed and selected from a total of 78 submissions. The papers are organized in topical sections on application multicast support, anycast and search in peer-to-peer networks, peer-to-peer systems, security and multicasting, multicast mechanisms,...